Hypoiodite oxidation

The synthesis of the four monocarboxylic acids of dibenzothiophene has been recorded in the previous review. However, several modified preparations have since been described. Ethyl 1-dibenzothiophene-carboxylate has been synthesized from 2-allylbenzo[6]thiophene (Section IV,B, 1) hydrolysis afforded the 1-acid (57% overall). In a similar manner, 3-methyl-1-dibenzothiophenecarboxylic acid was obtained from the appropriately substituted allyl compound. This method is now the preferred way of introducing a carbon-containing substituent into the 1-position of dibenzothiophene. 2-Dibenzothiophenecarboxylic acid has been prepared by oxidation of the corresponding aldehyde or by sodium hypoiodite oxidation of the corresponding acetyl compound. Reaction of 2-acetyldibenzothiophene with anhydrous pyridine and iodine yields the acetyl pyridinium salt (132) (92%), hydrolysis of which yields the 2-acid (85%). The same sequence has been carried out on 2-acetyldibenzothiophene 5,5-dioxide. The most efficient method of preparing the 2-acid is via carbonation of 2-lithio-... 

Bromine (hypobromite) and hypoiodite oxidations are particularly useful for the preparation of aldonic acids from aldoses and of aldaric acids from glycuronic acids. Primary alcohol groups also undergo oxidation by these reagents, although this conversion is of less value glycosides can thus be converted into glycosiduronic acids, and alditols into aldoses and aldonic acids. 

Alkaline hypoiodite oxidizes aldoses, under carefully controlled conditions, almost quantitatively to aldonic acids (see preceding chapter). Measurement of the iodine consumed permits quantitation of the amount of aldose originally present [Eq. (19)]. 

P. V. Peplow and P. J. Somers, Structural analysis by hypoiodite oxidation of periodate-oxidised carbohydrates, Carbohydr. Res., 22 (1972) 281-291. 

The barium salt from the methanol-hypoiodite oxidation of 7.5 g. (0.05 mole) of D-xylose was suspended in a small amount of water and decomposed with sulfuric acid. The barium sulfate was filtered and the solution concentrated to a sirup at reduced pressure. To the sirup dissolved in a mixture of 25 ml. of ethanol and 125 ml. of butanol, 4.6 g. (0.025 mole) of o-phenylenediamine dihydrochloride and 2.4 g. (0.022... 

Hypoiodite oxidation of 5-amino-5-deoxy-D-glucopyranose (45) gives 5-amino-5-deoxy-D-glucono-l,5-lactam. Hydrogenation (over... 

Kooiman separated exocellular amylose formed in liquid media at pH < 5 by Cryptococcus albidus and Cryptococcus laurentii var. flavescens NRRL Y-1401 from a polysaccharide containing D-man-nose, D-xylose, and D-glucuronic acid. X-Ray diffraction patterns of the retrograded amyloses were identical with that of tuber starch (B modification). Periodate oxidation, optical rotational measurements, and hypoiodite oxidation data suggested a linear a-D-(l—>4)-linked structure having a chain length of about 44 units for the Cr. albidus amylose. Cryptococcus neoformans produces a crystalline amylose that was isolated by the method of Schoch. It has an iodine value and alpha- and hefa-amylase hydrolysis characteristics similar to those of corn amylose. 

Up to pH 9 the iodine-iodide half-reaction is independent of pH. From pH 9 to 11 the formation of hypoiodite is appreciable but, since hypoiodite oxidizes arsenic(III) to arsenic(V) stoichiometrically,... 

Kline and Acree studied the hypoiodite oxidation extensively. The alkali and iodine were both added in small portions throughout the reaction. In this manner the concentration of sugar relative to the sodium hypoiodite was kept at a level favorable to the sugar oxidation (reaction 14). At the end of the reaction, the formation of iodate increased rapidly (reaction 15), taking precedence over the oxidation of ketoses and non-reducing sugars. 

With chlorous acid as the main oxidizing agent, the reaction is slow in neutral solution and becomes faster under acidic conditions. A solution containing equimolar amounts of sodium chlorite and acetic acid affords a slightly faster rate of oxidation for a-n-glucopyranose than for the 8-d anomer. Thus, the reaction appears to follow a different path from that of the bromine-water and the hypoiodite oxidations, and to be similar to that of cyanohydrin formation. ... 

Alkaline-hypoiodite oxidation of partially-bleached, sulfite wood-pulps decreases the alkali sensitivity. " Chlorous acid treatment of overbleached and of overchlorinated sulfite pulps also increases the alkali stability. "... 

Bromine and hypoiodite oxidations are particularly suitable for the preparation of aldonic acids from aldoses. Similarly, uronic acids are converted to saccharic acids. Of less value is the oxidation of primary alcoholic to aldehydic groups. In this manner, glycosides can be converted to uronides and polyols to aldoses and aldonic acids. 

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